1. Field of the Invention
The present invention relates generally to electrophotographic image forming devices and more particularly to angled toner paddles for a replaceable unit of an image forming device.
2. Description of the Related Art
In electrophotographic image forming devices, one or more replaceable toner cartridges may be used to supply toner to the device for printing onto sheets of media. When a toner cartridge is installed in an image forming device, the toner cartridge supplies toner stored in a reservoir within the toner cartridge through an outlet port on the toner cartridge to a corresponding inlet port in the device. Toner cartridges often include toner agitators, paddles or augers within the reservoir that fluff and mix the toner to prevent it from clumping and that move the toner to the outlet port.
For example, a first prior art toner cartridge 10 is shown in FIG. 1A with an end wall removed to more clearly illustrate the internal components of toner cartridge 10. Toner cartridge 10 is cylindrically shaped and includes a rotatable metal helix 12 within a toner reservoir 14 of the cartridge 10. As metal helix 12 rotates, it contacts an interior surface 16 of toner cartridge 10 and moves toner in reservoir 14 toward an outlet port near an end wall 18 of toner cartridge 10. However, metal helix 12 is rigid and does not conform to the shape of interior surface 16. As a result, metal helix 12 leaves a large amount of residual toner in reservoir 14 and is noisy when it rotates.
FIG. 1B shows a second prior art toner cartridge 20 with an outer wall removed to more clearly illustrate the internal components of toner cartridge 20. Toner cartridge 20 includes a molded plastic paddle 22 within a toner reservoir 24 of the cartridge 20. Paddle 22 includes a series of plastic, curved arms 26 that extend away from a central shaft 28 and together form a segmented helix. Curved arms 26 contact an interior surface 30 of toner cartridge 20. As shaft 28 rotates, curved arms 26 move toner in reservoir 24 toward an outlet port 32 near an end wall 34 of toner cartridge 20. Curved arms 26 are rigid and do not conform to the shape of interior surface 30. As a result, paddle 22 tends to leave a large amount of residual toner in reservoir 24.
FIG. 1C shows a third prior art toner cartridge 40 with a top wall removed to more clearly illustrate the internal components of toner cartridge 40. Toner cartridge 40 includes a toner reservoir 42 having an auger 44 mounted in a trough 46 along the entire length of reservoir 42. A flexible toner paddle 48 in the form of a flexible plastic sheet is mounted on a rotatable shaft 50 that extends along the entire length of reservoir 42, substantially parallel to auger 44. Toner paddle 48 and shaft 50 are positioned in a portion of reservoir 42 next to trough 46 and separated from trough 46 by a wall 52 that extends part way up from the bottom of reservoir 42. As shaft 50 rotates, flexible toner paddle 48 wipes toner from an interior surface 54 of reservoir 42 and advances along the bottom of reservoir 42 toward wall 52. When the distal end of toner paddle 48 reaches the top of wall 52, toner paddle 48 flips toner into trough 46 as the distal end of toner paddle 48 disengages from wall 52 in an elastic manner. However, the flipping action of toner paddle 48 tends to generate noise. Residual toner also tends to accumulate below auger 44.
Further, the flow rates of toner from many toner cartridges often vary greatly depending on the amount of toner left in the toner reservoir. As a result, such toner cartridges often require metering systems in the image forming device downstream from the toner cartridge to control the flow rate of toner. These downstream metering systems impose additional manufacturing cost. Accordingly, an improved, cost-effective system for agitating and moving toner inside a toner cartridge is desired that reduces noise and residual toner amounts.